Instead of a compressor that is driven via an electromagnetic clutch by an internal-combustion engine used for traveling, some air conditioning systems for vehicles that travel by means of the power of an internal-combustion engine use an electric compressor in order to improve the reduced drivability caused by engaging and disengaging the electromagnetic clutch.
Furthermore, in recent years, in addition to vehicles that travel by means of an internal-combustion engine, vehicles that travel by means of the power of an electric motor, such as electric vehicles, hybrid vehicles, and fuel-cell vehicles, have been rapidly developed and launched onto the market. Many air conditioning systems for such vehicles that travel by means of the power of an electric motor use an electric compressor, which is driven by an electric motor, as a compressor for compressing and supplying a refrigerant.
As such conventional electric compressors, as shown in FIGS. 11 and 12, hermetic electric compressors 100 and 200 in which an electric motor 12 and a scroll compression mechanism 11 are installed in a housing 2 and integrated on the same shaft 14 are employed. Like many other electric compressors, the electric compressors 100 and 200 shown in FIGS. 11 and 12 are each structured such that a compression-mechanism housing 3 accommodating the scroll compression mechanism 11 and an electric-motor housing 4 accommodating the electric motor 12 are joined with a bulkhead member 5 disposed therebetween.
In the electric compressor 100 used for a vehicle that travels by means of an internal-combustion engine, as shown in FIG. 11, the front end and the rear end of the main shaft 14 of the electric motor 12 are supported by a large-diameter main bearing 18 that is formed of a ball bearing press-fitted into the bulkhead member 5 and a small-diameter sub-bearing 19 that is provided at the back of the electric-motor housing 4.
A rotor 16 that constitutes the electric motor 12 is provided at an intermediate portion of the main shaft 14 so as to rotate integrally therewith. In general, the rotor 16 is shrink-fitted onto the main shaft 14. Furthermore, the front end of the main shaft 14 is inserted into the compression-mechanism housing 3 and is coupled with a rotary compression member 23 that constitutes the scroll compression mechanism 11 so as to drive the rotary compression member 23.
In a case of the thus-structured electric compressor 100, a thrust load imposed on the main shaft 14 is received by the main bearing 18, which is dual press-fitted. Specifically, an outer race 18a of the main bearing 18 is press-fitted into a main-bearing bore part 5a formed in the bulkhead member 5, from the scroll compression mechanism 11 side, and a main-bearing journal part 14b formed on the main shaft 14 is press-fitted into an inner race 18b of the main bearing 18 from the electric motor 12 side, thereby performing positioning. Here, the expressions “press-fitting from the electric motor 12 side” and “press-fitting from the scroll compression mechanism 11 side” mean that press-fitting is performed from either side of the bulkhead member 5 and from either side of the main bearing 18 but do not mean that press-fitting is performed inside the housing 2 of the electric compressor 100. In practice, each press-fitting is performed when the bulkhead member 5, the main bearing 18, and the main shaft 14 are outside the housing 2 of the electric compressor 100.
In the case of an electric compressor to be installed in a vehicle that travels by means of the power of an electric motor, as shown in FIG. 12, it is considered that a needle bearing is used as the main bearing 18 in order to reduce the weight, and a ball bearing, serving as the sub-bearing 19, is press-fitted to receive a thrust load imposed on the main shaft 14 (for example, PTL 1).
In PTL 1 or the electric compressor 200 shown in FIG. 12, the assembly order of the housing 2 main body, the main shaft 14, and the sub-bearing 19, which is formed of a ball bearing, is as follows. Specifically, first, the outer race 19a of the sub-bearing 19 is press-fitted into the sub-bearing bore part 4c provided in the housing 2 main body, from the scroll compression mechanism 11 side. Next, the sub-bearing journal part 14c of the main shaft 14 is press-fitted into the inner race 19b of the sub-bearing 19 from the scroll compression mechanism 11 side. At this time, it is necessary to use an assembly jig to support and press-fit the sub-bearing 19 from the rear end side of the main shaft 14 (the right side in FIG. 12).